Your local gas station probably offers you 3 levels of gasoline, like gold, silver and bronze. These typically have different levels of octane in them and you will generally get a little better mileage for the more expensive type.

In addition to different octane levels there are many different additives that can be in a companies brand of gasoline and this differentiation can have a big impact on your vehicle.

One type of additive is a detergent which generally cleans your engine. Without some level of detergents engine deposits form and this causes reduced fuel efficiency, acceleration and power as well as increasing emissions and rough idling.

zone-car.com

Your assumptions are incorrect.

If the engine in your car is designed for high octane fuel, you -must- use it or risk damage to the engine, though lately modern engine control systems can protect the engine from the idiot filling it with improper fuel. Some engines that are designed for high octane fuel (premium) do return better mileage with that fuel. I know the Nissan VQ engine will return mileage high enough on premium to offset the lower cost of using "mid-grade" (the engine is rated for 91 octane and higher but premium is "recommended"). In other words, it's actually cheaper to use premium in that engine. However, this cannot be just blanket stated for any engine design.

If you put high octane fuel in an engine that is designed for low octane, you will very likely waste fuel. It will not have time to burn fully in the combustion chamber because the pressure and therefore the temperature is not high enough, and will finish burning in the exhaust manifold and cat., which will result in -poorer- mileage. And yes, I've measured it. However, again, you can't make blanket generalizations for all engines. They operate differently with different fuels.

Additives in general will lower fuel economy as they displace some usable energy fuel products in the fuel. -IF- they do actually work to clean the engine interior (which is debatable - some work, some are placebos) then they may increase -overall- fuel economy - measured over years. An example is the addition of ethanol, the use of which will often result in a cleaner engine. However, ethanol contains about 35% less energy when burned, so if you add, say, 10% to gasoline, you will loose about 3.5% of the energy of a fuel with "pure" gasoline. Therefore you will get poorer mileage.

Pearl is a
2007 Driftwood Pearl Prius
Package "B" (everything but leather, nav, and rear camera)

higher octane fuels typically have less energy per gallon available, therefor lower mpgs.

and what he said.

also, no blanket statements are ever correct.

2000 Honda Insight. Kenwood MP3 head unit, Blaupunkt door speakers, dual Cobalt amps, 3 MTX stealth subs, 4th very-high-mounted brake light, Sumitomo tires, yellow-top, hot induction air mod, tinted, SG2, MIMA, center armrest.


best tank 82 mpg

David and Haf are correct. This is commonly misunderstood. Many think "higher octane means better gas, and better for your engine, too". Not true.

IF
the engine is designed to run optimally on regular (and most non-high-performance engines ARE),
THEN
putting mid-grade or premium or racing fuel or octane boosters, etc is a waste of money and usually results in less MPG, not more. And it will NOT increase performance.

Only if the engine is designed to operate on Premium should you bother to actually USE premium. And in that case, you'd better use it! Engine damage can (and often does) occur. Engines designed this way state "Premium Unleaded Only."

Newer engines may state "Premium Unleaded Recommended." Like David said, the engines stating "Premium Unleaded Recommended" are case-by-case studies. Premium fuel WILL likely improve performance. It may also improve MPG. And it may be worth the difference in cost per mile (or the extra boost in performance may be worth any extra cost per mile) for the Premium. You have to do your own comparison with these engines. It's good to have choices, in this case.

Steve

STOP terrorism - Drive a HYBRID

Vehicles:
350 miles a week ------------ 2006 HCH II, Magnetic Pearl, w/NAVI (born on May 25, 2006)
350 miles a month ---------- 2003 Mazda Tribute ES-V6
350 miles a year (for now) - 1986 Mercedes 560SL

These four automakers decided to do something about this problem and create their own class of gasoline called 'Top Tier Detergent Gasoline', containing a higher level of detergents. This was meant to keep vehicle owners happier with better engine performance and wear and allow gasoline marketers the opportunity to distinguish their product from the competition.

In 1994 a few gasoline distributors adopted this new industry standard and since then it has expanded across North America. Current retailers are QuikTrip, Chevron, Conoco, Phillips, 76, Shell, Entec Stations, MFA Oil Company, Kwik Trip/Kwik Star, The Somerset Refinery, Chevron-Canada, Aloha Petroleum, Tri-Par Oil Company, Shell-Canada, Texaco, Petro-Canada and Sunoco-Canada.

I personally discovered this gas by trying the 'silver' gas out at Shell. I thought it would just increase performance for this one fillup due to the higher octane. Surprisingly, later fillups with the cheaper bronze gasoline still saw a 5% increase in mileage, not bad for an aging 5 year old car.

This gasoline is good for new cars as it keeps the engine running optimally and especially good for older cars with engine deposits.

zone-car.com

You might find some of our earlier discussions useful:
http://www.greenhybrid.com/discuss/f...66/#post137209
http://www.greenhybrid.com/discuss/f...tml#post124496

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

This thread is a disguised advertisement, and a few people got sucked into it. I'm asking a moderator to remove it.

Huh?

I'm pretty confident in my gasoline energy study data. It seems to be reproducible and there does appear to be an improvement in MPG, slight but real. As for additives, I have no data or even an idea of how best to approach testing.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

Bob, gpsman is referring to the OP, not YOUR contributions.
Gpsman could be right here, as some of the assumptions made were wrong and misleading, but I think the OP was just misreading other advertisers marketing about regular vs. mid-grade vs. premium gasolines.
The Top-Tier debate is ongoing, and potentially has merit. Many of us know the original INTENT - the debate is over whether it really does matter (or matter any more). SOME gasolines certainly are better than others. This may depend on where you live, however, as delivery practices vary.

Steve

STOP terrorism - Drive a HYBRID

Vehicles:
350 miles a week ------------ 2006 HCH II, Magnetic Pearl, w/NAVI (born on May 25, 2006)
350 miles a month ---------- 2003 Mazda Tribute ES-V6
350 miles a year (for now) - 1986 Mercedes 560SL

Question.. Why does lower octane gasoline advisable for Hybrid vehicles??

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